Method and system for heating a bed of hydrocarbon- containing rocks

ABSTRACT

Hydrocarbon-containing rocks (e.g, mined oil shale or mined coal or tar sands) are introduced into an excavated enclosure (e.g. a pit or an impoundment) to form. a bed of rocks therein, One or more heaters (e.g. molten salt heaters) are operated to pyrolyze kerogen or bitumen of the rocks. In some embodiments, a hydrocarbon reflux loop is maintained within the enclosure to convectively heat the hydrocarbon-containing rocks by boiling hydrocarbon liquids from a reservoir at the bottom of the enclosure so that vapor passes to the top of the enclosure, condenses, and falls back through the bed. Alternatively or additionally, the rocks may be heated by heaters embedded within wall(s) and/or a floor of the enclosure. Some embodiments relate to techniques for upgrading mined coal to recover both hydrocarbon pyrolysis fluids and upgraded coal (e.g. anthracite coal).

FIELD OF THE INVENTION

Embodiments of the present invention relate to methods and apparatus forheating a bed of kerogen-containing or bitumen-containing rocks, forexample, to produce pyrolysis fluids therefrom.

DESCRIPTION OF RELATED ART

Hydrocarbons obtained from subterranean formations are often used asenergy resources, as feedstocks, and as consumer products. Concerns overdepletion of available hydrocarbon resources and concerns over decliningoverall quality of produced hydrocarbons have led to development ofprocesses for more efficient recovery, processing and/or use ofavailable hydrocarbon resources. In situ processes may be used to removehydrocarbon materials from subterranean formations that were previouslyinaccessible and/or too expensive to extract using available methods.Chemical and/or physical properties of hydrocarbon material in asubterranean formation may need to be changed to allow hydrocarbonmaterial to be more easily removed from the subterranean formationand/or increase the value of the hydrocarbon material. The chemical andphysical changes may include in situ reactions that produce removablefluids, composition changes, solubility changes, density changes, phasechanges, and/or viscosity changes of the hydrocarbon material in theformation.

Large deposits of heavy hydrocarbons (heavy oil and/or tar) contained inrelatively permeable formations (for example in tar sands) are found inNorth America, South America, Africa, and Asia. Tar can be surface-minedand upgraded to lighter hydrocarbons such as crude oil, naphtha,kerosene, and/or gas oil. Surface milling processes may further separatethe bitumen from sand. The separated bitumen may be converted to lighthydrocarbons using conventional refinery methods. Mining and upgradingtar sand is usually substantially more expensive than producing lighterhydrocarbons from conventional oil reservoirs.

Retorting processes for oil shale may be generally divided into twomajor types: aboveground (surface) and underground (in situ).Aboveground retorting of oil shale typically involves mining andconstruction of metal vessels capable of withstanding high temperatures.The quality of oil produced from such retorting may typically be poor,thereby requiring costly upgrading. Aboveground retorting may alsoadversely affect environmental and water resources due to mining,transporting, processing, and/or disposing of the retorted material.Many U.S. patents have been issued relating to aboveground retorting ofoil shale. Currently available aboveground retorting processes include,for example, direct, indirect, and/or combination heating methods.

SUMMARY OF EMBODIMENTS

Embodiments of the present invention relate to apparatus and methods forheating hydrocarbon-containing matter (e.g. tar sands orkerogen-containing rocks such as pieces of coal or pieces of oil shale)within an enclosure such as a pit or an impoundment or a container.Hydrocarbon-containing rocks are introduced into the enclosure to form abed (e.g. a packed-bed) of rock therein. Oxygen may be evacuated (e.g.under vacuum or by means of an inert sweep gas) to create asubstantially oxygen-free environment within the enclosure. In differentembodiments, the enclosure may be a pit, or an impoundment or acontainer. The enclosure may be entirely below ground level, partiallybelow and partially above, or entirely above ground level.

Operation of heaters in thermal communication with thehydrocarbon-containing rocks may sufficiently heat the rocks to convertkerogen or bitumen thereof into pyrolysis formation fluids comprisinghydrocarbon pyrolysis fluids. The formation fluids may be recovered viaproduction conduits, or via a liquid outlet located at or near thebottom of the enclosure and/or via a vapor outlet located near the topof the enclosure, or in any other manner.

After they exit the pit, the NGL (natural gas liquids) such as propaneand butane may be separated from the methane and ethane gases because ofthe high economic value of NGL. Hydrogen may also be separated from theproduced gases and used in upgrading of the produced shale or coal oils.

Some embodiments relate to apparatus and methods of heating beds ofhydrocarbon-containing rocks (e.g. piece of coal or of oil shale, or tarsand) in a manner that has an improved efficiency and/or minimizescapital costs and/or accelerates the heating so as to allow forexpedited recovery of the hydrocarbon pyrolysis fluids. Towards thisend, it is now disclosed techniques whereby thermal energy istransferred to the hydrocarbon-containing rocks from molten salt heatersand/or from immersed heaters and/or in a system where convection is thedominant heat transfer mechanism.

Some embodiments relate to apparatus and methods for maximizing aneconomic and/or an environmental value of the thermally treatedhydrocarbon-containing rocks for example, by upgrading coal in a mannernow disclosed. Some embodiments relate to apparatus structured forrelatively easy removal of thermally treated rocks (e.g. upgraded coal)from the container - for example, in a manner that minimizes the cost ofremoval or that facilitates re-use of the container.

In some embodiments related to heat convection and efficient heattransfer, thermal energy is transferred to the hydrocarbon-containingrocks primarily by liquid-immersed heaters deployed at or near thebottom of the container. In particular, the heaters may be immersed in areservoir of hydrocarbon liquids (e.g. having a boiling point between300 and 400 degrees) located at or near a bottom of the container. Thedirect thermal coupling between the heaters and the liquid in directcontact with the heaters significantly (e.g. by one or more orders ofmagnitude) increases an efficiency of heat transfer from the heaters toheat the hydrocarbon liquid of the immersing reservoir.

The hot hydrocarbon fluid (i.e. liquid or vapors boiled therefrom) ofthe reservoir upwardly migrates to locations above or near the top ofthe bed—for example, via one or more vertical conduits that verticallytraverse the rock bed. The presence of the vertical conduits helps tomaximize the fraction of thermal energy from the heaters that migratesdirectly to the top of the bed of particles.

The upward migration of hydrocarbon fluid (e.g. via the verticalconduit(s)) convectively transfers thermal energy supplied by theimmersed heaters to these locations above or near the top of the bed.When this hydrocarbon fluid subsequently falls downwards through therock bed, this thermal energy supplied by the immersed heater isconvectively transferred to an interior of the rock bed.

In some embodiments, the walls of the vertical conduit(s) aresubstantially fluid-tight and/or thermally insulated so that most, orsubstantially an entirety, of the thermal energy of thereservoir-originating hydrocarbon fluids remains within the verticalconduit(s) during the upward migration of the hydrocarbon fluids.Because a relatively small fraction of thermal energy transferred to thebed during upward migration of the hot hydrocarbon fluids, it may besaid that the primary heat transfer mechanism of thermal energy from theheaters to the bed of particle is downward heat convection. Oneadvantage of relying specifically on heat convection is that it isassisted by gravity and may be much more efficient.

Some embodiments of the present invention provide two efficiency-relatedfeatures: (i) transfer of thermal energy to hydrocarbon liquids from theimmersed heaters; and (ii) gravity-assisted downward heat convection tothe bed of particles.

Some embodiments of the present invention relate to convectivere-boiling loops. In these embodiment, thermal energy from the immersedheaters boils liquids of the reservoir into condensable hydrocarbonvapor - for example, the liquid may enter the vapor phase beforeentering the vertical conduit or within the vertical conduit. Because ofthe relatively low density of hot hydrocarbon vapors, gravity drivesupwards migration of the hydrocarbon vapors. The hydrocarbon vapor maycondense (i) above and/or (ii) within the rock bed—e.g. in an upper halfthereof or as the vapor moves downwards in the bed. In the later case,condensation of hydrocarbon vapors within the rock transfersphase-change enthalpy to the hydrocarbon rocks, further increasing athermal efficiency of the heating process.

As an alternate to a re-boiling loop where buoyancy drives upwardsmigration of the heated gas-phase hydrocarbon fluids from the reservoir,it is possible to employ a gas lift or other pumping system to driveupward migration of liquid-phase hydrocarbon fluids from the reservoirfrom the bottom of the container to locations above or near the top ofthe rock bed. In these embodiments, hydrocarbon liquids are sent throughthe vertical conduits and then fall back through the bed. In bothre-boiling embodiments (i.e. where vapor migrates upwards through thevertical conduits) as well as liquid embodiments (i.e. where hydrocarbonliquid or a multi-phase flow primarily comprising liquids flow upwardsthrough the conduit), the bed of rocks may be heated such that kerogenor bitumen of upper locations of the particle beds is pyrolyzed beforethat of lower locations of the particle bed. Thus, in some embodiments,a downwardly-moving pyrolysis front may be observed.

Although not a requirement, in one preferred embodiment, the immersedheaters are molten salt heaters. Molten salt heaters may be preferredbecause of their high thermal efficiency and uniform temperatures.

Furthermore, it is noted that molten salt may be employed as a heattransfer fluid in heaters that are not necessarily immersed heaters. Forexample, as discussed below, molten salt heaters may be deployedsubstantially at a wall of the enclosure or within a wall thereof.

In some embodiments, the enclosure may be sealed after the kerogen orbitumen is pyrolyzed and hydrocarbon pyrolysis fluids are recovered.Alternatively, the post-pyrolysis rocks may be recovered from thecontainer and the container may be reused. For example, it is possibleto sufficiently pyrolyze bituminous coal within the container so as toupgrade the bituminous coal to much more valuable and moreenvironmentally benign anthracite coal.

In some embodiments, the apparatus for pyrolyzing hydrocarbon-containingrocks may substantially lack horizontally-oriented heaters that aredeployed in locations significantly above the floor of the enclosure, orfacilitate the removal of upgraded coal from the enclosure. For example,advection heaters embedded within or outside the walls or within a floorof the enclosure may be used to heat the hydrocarbon-containing rocks topyrolysis temperatures.

In some embodiments, horizontal heaters that can maintain a constantpreselected temperature along a long length are utilized. The heatersmay be electrical heaters such as Curie heaters or SECT heaters. Theheaters may be pipes heated by a heat transfer media such as moltensalts, heated oils, and heated gases such as CO₂, nitrogen, or steam orcombustion air.

Heated molten salts may be circulated through the pipes to boil the oilin the lower section to pyrolyze the oil shale or coal in the pit. Theadvantages of the molten salt heating are the extremely high energyefficiency and the high heat transfer efficiency of molten salt. Onlysmall diameter piping is required and uniform temperatures are achievedover long lengths. Hence the length of the surface pit may be very long,for example at least 30 meters or at least 100 meters or at least 200meters or at least 500 meters longer. The piping may also be loopedinside the pit so that the exterior piping manifold has fewerconnections with fewer chances of leaks.

In the case of coal, the top seal of the pit or pile is opened afterpyrolysis to remove the devolatilized coal. This coal may be morevaluable than the initial coal because it has higher carbon content,higher calorific value, ultra lower moisture and volatiles, and lowersulfur. After removing the post-treatment coal, the pit can be refilledwith fresh coal for the next pyrolysis. The post-pyrolysis coal may alsobe steam washed in the pit while still warm to remove ash from the coaland further upgrade the coal to the highest grade metallurgical coal.Circulating steam may achieve both the cooling and washing of the coal.

The pit may be constructed below grade level using earth-movingequipment. The pit may be lined with clay, such as bentonite, to renderthe walls and bottom substantially impermeable to liquids and vapors. Itmay be desirable to choose a location where the surface geology is anaturally-occurring clay so that lining the pit is unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist in the understanding of the invention and for purposes ofillustrative discussion, some embodiments are herein described, by wayof example only, with reference to the accompanying drawings and images.In this regard, the description taken with the drawings makes apparentto those skilled in the art how embodiments of the invention may bepracticed. Dimensions of components and features shown in the figuresare chosen for convenience and clarity of presentation and are notnecessarily shown to scale. The drawings are not to be considered asblueprint specifications.

FIGS. 1A-1B, 5-12 and 17 illustrate reflux-based systems where repeatedboiling of hydrocarbon liquids of a reservoir convectively transfersthermal energy from heater(s) immersed within the liquid reservoir tovarious locations of the rock bed.

FIGS. 2, and 13-18 relate to systems for pyrolysis ofhydrocarbon-containing rocks (e.g. mined oil shale or mined coal or tarsands) arranged in a rock bed in an interior of an excavated enclosureby wall-embedded heaters.

FIGS. 4A-4B relate to methods for re-using an interior of an excavatedenclosure. FIGS. 4B and 19-22 relate to techniques for upgrading minedcoal within an excavated enclosure.

FIGS. 3 and 23-24 relate to systems where a rock bed ofhydrocarbon-containing rocks is heated by horizontal molten salt heaterstraversing the rock bed.

DETAILED DESCRIPTION OF EMBODIMENTS

Overview

Embodiments of the present invention relate to apparatus and methods forheating hydrocarbon-containing matter (e.g. tar sands orkerogen-containing rocks such as pieces of coal or pieces of oil shale)within an enclosure such as a pit or an impoundment or a container.Hydrocarbon-containing rocks are introduced into the enclosure to form abed (e.g. a packed-bed) of rock therein. Oxygen may be evacuated (e.g.under vacuum or by means of an inert sweep gas) to create asubstantially oxygen-free environment within the enclosure. In differentembodiments, the enclosure may be a pit, or an impoundment or acontainer. The enclosure may be entirely below ground level, partiallybelow and partially above, or entirely above ground level.

Operation of heaters in thermal communication with thehydrocarbon-containing rocks may sufficiently heat the rocks to convertkerogen or bitumen thereof into pyrolysis formation fluids comprisinghydrocarbon pyrolysis fluids. The formation fluids may be recovered viaproduction conduits, or via a liquid outlet located at or near thebottom of the enclosure and/or via a vapor outlet located near the topof the enclosure, or in any other manner.

Examples of hydrocarbon-containing rocks are kerogen-containing rocks(e.g. mined oil shale or mined coal) and bitumen-containing rocks (e.g.tar sands).

FIGS. 1A-1B, 5-12 and 17 illustrate reflux-based systems where repeatedboiling of hydrocarbon liquids of a reservoir convectively transfersthermal energy from heater(s) immersed within the liquid reservoir tovarious locations of the rock bed. FIGS. 2, and 13-18 relate to systemsfor pyrolysis of hydrocarbon-containing rocks (e.g. mined oil shale ormined coal or tar sands) arranged in a rock bed in an interior of anexcavated enclosure by wall-embedded heaters. FIGS. 4A-4B relate tomethods for re-using an interior of an excavated enclosure. FIGS. 4B and19-22 relate to techniques for upgrading mined coal within an excavatedenclosure. FIGS. 3 and 23-24 relate to systems where a rock bed ofhydrocarbon-containing rocks is heated by horizontal molten salt heaterstraversing the rock bed.

FIGS. 1A-1B is a schematic diagram of a horizontal cross-section of areflux-based surface pit system for pyrolyzing a bed ofhydrocarbon-containing rocks arranged in a rock bed 110—for example, apacked bed of rocks arranged according to any packing (e.g. randompacking). In the example of FIGS. 1A-1B, a plurality of heaters 134arranged substantially at the bottom of the pit heat an interior of thepit so as to heat the hydrocarbon-containing rocks of the rock bed 110.As will be discussed below, for the examples of FIG. 1A-1B, heatconvection is a significant mechanism of transferring thermal energyfrom heaters 134 of rock bed 110.

As illustrated in FIGS. 1A-1C, heaters 134 are immersed within areservoir 114 of hydrocarbon liquids at the bottom of the pit. Heatingof the liquid-phase hydrocarbon fluids of reservoir 114 by immersedheaters 118 drives the hydrocarbon fluids upwards—e.g. by vaporizing thefluids or by reducing a density of hydrocarbon liquids. Theupwardly-driven heated hydrocarbon fluids (i) enter vertical chimney 126via a lower opening 144 thereof; (ii) migrate upwards through verticalchimney 126 to substantially vertically traverse rock bed 110 (seeupwardly migrating condensable hydrocarbon vapor (UMCHCV) and (iii) exitvertical chimney via an upper opening 148 thereof.

The heated hydrocarbon fluids may vaporize either before enteringchimney 126 or therein. Thus, as illustrated FIGS. 1A-1B, hydrocarbonvapors derived by boiling liquids of reservoir 114 migrate upwardsthrough vertical chimney 126—these upwardly migrating vapors are labeledUpwardly Migrating Condensable Hydrocarbon Vapor (UMCHCV). Because aresistance to fluid flow within the chimneys 126 is significantly lowerthan within the rock bed 110, the presence of the chimneys 126 maysignificantly increase a rate at which thermally energy convectively andupwardly migrates to the top of rock bed 110.

Upon exiting vertical chimney 126, the hydrocarbon vapors may condenseback into the liquid phase upon contacting a surface whose temperatureis below its boiling point at that pressure. As condensed hydrocarbonliquids fall back downwards through the rock bed 110 (i.e. labeledDownwardly Migrating Hydrocarbon Liquids (DMHCL)), they convectivelyheat the rocks of rock-bed 110—for example, sufficiently to pyrolyzebitumen or kerogen thereof.

Thus, FIGS. 1A-1B relate to a reflux/reboiling loop whereby hydrocarbonliquids are repeatedly boiled to efficiently and convectively transfer(e.g. over relatively ‘large distances’) thermal energy from immersedheaters to various locations of rock bed 110 including those atrelatively ‘high’ elevations. In the example of FIG. 1A-1B, a majorityor substantial majority of upward vapor migration occurs within thevertical chimneys where resistance to fluid flow is at least 10 times orat least 100 times or at least 1,000 times an average fluid flowresistance observable within rock bed 110—thus, the presence of thechimneys 126 may significantly increase the efficiency of convection ofthermal energy from the immersed heaters to the rock bed 110.

Thus, one advantage of the system of FIGS. 1A-1B is the shorter amountof time required to pyrolyze kerogen or bitumen of the rock bed.

FIG. 2 illustrates one example of a surface pit system for thermallytreating a rock bed 110 of hydrocarbon-containing rocks within aninterior of an excavated enclosure (e.g. pit or impoundment) that isheated by molten salt heaters. In the specific example of FIG. 2,vertical molten salt heaters 178 (VMSH) are arranged within a tall, thinchamber 184—i.e. a ratio between a height of chamber 184 and at leastone horizontal dimension thereof (e.g. a lesser horizontal dimension)may be at least 5 or at least 10. Rocks of rock bed 110 are arranged inthe interior of a chamber of an enclosure (e.g. a pit).

At least one wall of the excavated enclosure containing rock bed 110 isheated by the vertical molten salt heaters 178. In the example of FIG.2, a primary mechanism of heating of rock bed 110 is by transfer ofthermal energy from the walls of the enclosure (i.e. which are heated bythe ‘embedded heaters’) to rock bed 110.

As will be discussed below, one advantage of the apparatus of FIG. 2 isefficiency due to the use of molten salt, an extremely efficientheat-transfer fluid. FIG. 3 is another example of a surface pit systemincluding molten salt heaters—in the example of FIG. 3, the molten saltheaters comprise horizontal conduits that pass through a bed ofhydrocarbon-containing rocks. Although not explicitly stated above, isfurther noted that the immersed 134 of FIGS. 1A-1B may be molten saltheaters.

Reference is made once again to FIG. 2. By relying primarily onwall-embedded heaters rather than heaters located within rock bed 110(for example, horizontal conduit heaters that traverse rock bed 110), itmay be significantly easier to remove post-pyrolysis rocks to re-use thepit to pyrolyze another batch of hydrocarbon-containing rocks. As willbe discussed in greater detail below, in some embodiments, thesepost-pyrolysis rocks may be a valuable and/or environmentally friendlysolid hydrocarbon resource.

FIG. 4A is a flowchart of a routine for re-using an enclosure after ithas been used to pyrolyze kerogen or bitumen of rocks of a rock-bed.FIG. 4B relates to the specific case where (i) pieces of minedbituminous coal form a rock-bed within an enclosure; and (ii) thebituminous coal is upgraded to anthracite coal within the enclosure—forexample, heaters are operated to provide the requisite time-temperatureheating history. As will be discussed below, (i) anthracite coal is muchmore environmentally friendly and potentially more valuable thanbituminous coal and (ii) in some embodiments, the techniques FIG. 4B mayrequire subjecting the bituminous coal to a more rigoroustime/temperature history than would be required for situations where oneis only interested in obtaining hydrocarbon pyrolysis fluids.

For the present disclosure, when the temperature of an object orlocation is ‘significantly increased,’ this requires an increase of atleast 25 degrees Celsius or at least 50 degrees Celsius.

For the present disclosure, an ‘excavated enclosure’ refers toartificially dug pit or a natural pit (i.e. modified in some manner) orto a pile of soil/earth formed or modified by excavation—e.g. to form animpoundment at least partly above-ground.

For the present disclosure, a ‘substantial majority’ refers to at least75%.

For the present disclosure, when a fluid (e.g. molten salt or any otherfluid) is ‘hot’ a temperature thereof is at least 200 degrees Celsius orat least 300 degrees Celsius.

Reflux Based Systems

For the present disclosure, a ‘hydrocarbon reflux loop’ describes the(i) boiling of hydrocarbon liquid into condensable hydrocarbon vapors;(ii) the upward migration of the hydrocarbon vapors; (iii) thecondensation of the hydrocarbon carbon vapors back into liquid at ahigher location than where the liquid was boiled (e.g. above the rockbed or substantially at a top of the rock bed); and (iv) gravity-drivendownward migration (i.e. ‘falling’) of the hot hydrocarbon liquids backdown through the rock bed to convectively transfer thermal energy fromthe hydrocarbon liquids to the rocks of the rock bed. It is requirementof the ‘reflux loop’ for the condensed hydrocarbon liquids to besubsequently re-boiled back into hydrocarbon vapors to repeat the upwardmigration, condensation, and downward migration to convectively transferthermal energy to the rocks.

As noted above, FIGS. 1A-1B, 5-12 and 17 illustrate reflux-based systemswhere repeated boiling of hydrocarbon liquids of a reservoirconvectively transfers thermal energy from heater(s) immersed within theliquid reservoir to various locations of the rock bed.

In order to create an anoxic environment within the enclosure (e.g.within the ‘pit’), the pit may be sealed. In the example of FIG. 1A, thepits is sealed from the top by substantially-fluid tight cover 138 (e.g.comprising soil). Furthermore, a presence of clay liner 152 may retainfluids within an interior of the excavated enclosure. A presence of athermal insulator such as concrete liner 156 may retain thermal energywithin an interior of the excavated enclosure. As an alternative to theclay liner 152 and/or concrete liner 156 (i.e. which is illustrated invarious figures), it is possible (see, for example, FIG. 10B) to selecta location where the underlying source rock has a low permeability toretain fluids within the enclosure interior and/or is a good thermalinsulator to retain thermal energy within the enclosure. In yet anotherexample, it is possible to employ a freeze wall and/or wax wall and/orsulfur wall to retain fluids—this may be deployed adjacent to theexcavated enclosure or distanced therefrom. For example, a freeze wallor sulfur wall or wax wall structure may enclose a plurality ofexcavated enclosures.

As illustrated in FIG. 5, rock bed 110 is supported by a grating (e.g.steel grating 120) which is not fluid tight but which has a pore sizethat is significantly smaller than a characteristic size of the rocks ofrock bed 110. The small characteristic pore size of the grating is small(e.g. at most 10 cm prevents rocks of rock bed 110 from falling into andclogging up reservoir 114. Furthermore, in some embodiments a secondrock bed of non-pyrolyzable rocks (e.g. a tight gravel filter 122) mayalso serve this purpose.

As illustrated in FIGS. 5, an upper level 118 of reservoir 114 may bemaintained substantially above heaters 134 so that heaters 134 remainimmersed within reservoir 114. In some embodiments, the upper level 118is maintained substantially below an entirety of rock bed 110.

As noted above, once condensable hydrocarbon vapors exit from a top ofchimney 126 via upper opening 148, they may condense at locations at orabove a top of rock bed 110 but within the sealed excavated enclosure,e.g. due to the lower temperatures at the top of the enclosure. In someembodiments, in order to horizontally distribute the liquid-phasecondensed hydrocarbon fluids to various locations within the rock bed110, it may be useful to provide a liquid distribution system above rockbed 110 so as to distribute the condensate over a variety of horizontallocations of rock bed 110.

In the examples of FIGS. 6-8, an array of spreader tray(s) 220 arearranged substantially above rock bed 110. Condensation of hydrocarbonvapor above spreader tray causes hydrocarbon liquid (e.g. at or near aboiling point thereof) to accumulate in an ‘upper reservoir’ 214 on thespreader tray(s) 220. Because the upper reservoir 214 is supplied bycondensation of hydrocarbon vapor(s) that exits via upper opening 148 ofchimney 126, it may be said that upper reservoir 214 is supplied by thelower reservoir 114. Although multiple spreader trays 220 areillustrated in FIGS. 6-7 this is not a limitation and in someembodiments, a single spreader tray 220 (e.g. having multiple voids 224therein) may be arranged within the enclosure.

Hydrocarbon liquid falls through one or more voids 224 within or betweenspreader tray(s) and then falls through the rock bed 110. As illustratedin FIG. 7, the spreader tray assembly (e.g. including the void(s) 224)is useful for horizontally distributing the hydrocarbon liquid (i.e.derived from condensation above rock bed 110) throughout rock bed 110.

In the example of FIG. 8, each void is associated with a lip 228. Inorder for hydrocarbon liquid of upper reservoir 214 to flow downwardlythrough a given void, a level of upper reservoir 214 should exceed aheight of lip 228 above the spreader tray 220 to which it is attached.The presence of lip 228 around each void 220 helps to temporally smootha rate at which condensed hydrocarbon liquids flow down through void 220into bed 104. The presence of lip 228 helps to regulate an amount ofhydrocarbon liquid in upper reservoir

One salient feature provided by embodiments of the present invention isthe downward heat convention in an upper half of rock bed 110 that isdriven by heaters (e.g. immersed heaters) below rock bed 110. Thus,despite the fact that a majority or substantial majority of thermalenergy delivered to rock bed 110 comes from heaters below rock bed 110,it is possible to generate downward convection (i.e. by means of thevertical chimneys 126) in an upper half of rock bed 110.

In some embodiments, as a result of the downward heat convection (e.g.driven by thermal energy supplied by heaters 134 immersed within lowerhydrocarbon liquid reservoir 114), kerogen or bitumen ofhydrocarbon-containing rocks at the very top of rock bed 110 is heatedto pyrolysis temperatures before kerogen or bitumen of rocks at lowerlevels within the top half of rock bed 120. Thus, in some embodiments,and as illustrated in FIGS. 9A-9C, a downwardly moving pyrolysis frontmay be observed in an upper half of rock bed 110.

As noted above with reference to FIG. 4A, in some embodiments it isdesirable to reuse an excavated enclosure (e.g. pit or impoundment). Onefeature for such re-use is illustrated in FIG. 10A. Substantiallyvertical chimney 126 may be mounted to support grating 120 in a mannersuch that the vertical chimney is detachable. In the example of FIG.10A, chimney 126 may be mounted onto the grating so that a lower distalend of chimney 126 of a cap thereof it mounted into a pipe port. In oneexample, after mounting of chimney 126, rock bed 110 is formed byintroducing hydrocarbon-containing rocks into the excavated enclosure.This may be followed by heating of the rock bed—e.g. to pyrolyze kerogenor bitumen thereof. After pyrolysis, it is possible before removing amajority of rock bed 110 to (i) disengage a distal end of chimney 126 tothe mounted ports mounted onto the grating; (ii) pull vertical chimneys126 out of the excavated enclosure; and (iii) once the chimneys havebeen removed and there is substantially an absence of heaters and otherequipment in an interior of rock bed 110, scoop out rocks of rock bed110. As is the case with the wall-embedded heater embodiments discussedelsewhere with reference to FIGS. 2 and 13-18, the technique of FIG. 10Amay facilitate pit re-use and/or economic exploitation of post-pyrolysisrocks (e.g. upgraded coal) of rock bed 110.

Reference is now made to FIG. 10B. In the example of FIG. 10B, there isno need for a clay liner.

FIG. 11 is schematic illustration of yet another embodiment of thepresent invention. In the example of FIG. 11, the chimneys are situatedsubstantially at the walls of the excavated enclosure. This is incontract to the example of FIGS. 1A-1B and 5 where the chimneys aresurrounded by the rock bed 102.

Illustrated in FIG. 11, but applicable to all reflux-based embodimentsis apparatus for regulating a liquid level 118. A fluid level sensor andautomatic control valve maintain the level of the boiling oil above theheaters. As pyrolysis occurs, additional coal or shale oil liquidhydrocarbons above this level are produced via the automatic controlvalve through production pipes.

Outside the pit, the liquid hydrocarbons produced from the pit enter afractionation tower. There, coal or shale oil with a preselected boilingpoint cut is removed and drained into the bottom of the pit just abovethe boiling hydrocarbon liquid. This circulation from the fractionationtower constantly refreshes the boiling hydrocarbons at the bottom of thepit and maintains the composition of the boiling hydrocarbons at thedesired boiling point range.

For the present disclosure, when a rock bed is situated within anenclosure, an ‘external heater’ is a heater located outside of thechamber/region where the rock bed is situated. This is in contrast toheaters within the rock bed—for example, conduits which traverse therock bed.

During heating, a 118 level of reservoir covers the heater pipes. Thespacing between pipes is calculated to provide continuous boiling of theoil. Typical heater spacing may be, for example, 5 ft, 10 ft or greater.The heat transfer from the heater pipes immersed in oil may be 1000watts/ft, 5000 watts/ft, 10,000 watts/ft or higher. The optimal spacingmay be determined by numerical simulations or by scale modelexperimentation in the lab.

Heating of the coal or oil shale to pyrolysis temperatures is achievedvia a refluxing process where boiling hydrocarbon vapors condense on thecolder sections of the pit and impart the heat of vaporization. Liquidhydrocarbons return to the oil bath through the coal or oil shale matrixby gravity and capillary forces. The refluxing process may be enhancedby adding slotted conduits to provide preferential pathways for vaporflow to reach the colder section, as shown in FIG. 2. The conduits maybelocated along the sides and middle of the pit and may extend the lengthof the pit. Multiple rows of conduits may be added to further enhancethe refluxing process. Condensation may initially occur at or near thebottom of the pit and progress upward during the heating process. Theheating time of the pit to pyrolysis temperature will be determinedapproximately by the heat capacity of the packed coal in the pit dividedby the total heat input from all the heaters minus any heat losses tothe surrounding environment.

The hydrocarbon liquid of reservoir 114 that may be used for startingthe heating may be a diesel oil with a boiling point above 300° C. Theheater pipes should be heated to a temperature where the heater pipeskin temperature is higher than the boiling point of the oil but notabove 375° C. where coking of the diesel oil may occur. An optimumtemperature may be in the range 300-375° C., 325-370° C., or 340-360° C.When operating at the higher temperature ranges, the heater pipes may becoated with coke inhibitors such as silicates to prevent scale fromforming.

As the pyrolysis proceeds, the condensed hydrocarbon pyrolysis liquidswill mix with the diesel oil in the bottom of the pit. The boiling pointdistribution will gradually change to that of the shale oil or coal oil.If the boiling point distribution gets too elevated in temperature, itmay be desirable to circulate additional diesel cut into the bottomsection to maintain the boiling point in the above mentioned ranges.

As shown in FIG. 11, a fluid level sensor and automatic control valvemaintain the level of the boiling oil above the heaters. As pyrolysisoccurs, additional shale oil liquid hydrocarbons above this level areproduced via the automatic control valve through production pipes.

Outside the pit, the liquid hydrocarbons produced from the pit enter afractionation tower. There shale oil with a preselected boiling pointcut is removed and drained into the bottom of the pit just above theboiling hydrocarbon liquid. This circulation from the fractionationtower constantly refreshes the boiling hydrocarbons at the bottom of thepit and maintains the composition of the boiling hydrocarbons at thedesired boiling point range.

The pressure in the pit may be maintained at atmospheric pressure or atan elevated pressure (e.g. 1 to 3 atm.). The higher the pressure duringpyrolysis, the higher quality the oil and gas produced. The pressurethat can be maintained may be determined by the depth of the pit and theamount of soil added above the seal. Higher pressures improve the oilqualities but increase the possibility of gaseous leakage from the pit.

Maintaining pressure with non-condensable gases may also be used tocontrol the height of the refluxing process and thereby controlling thevolume of coal or oil shale being heated at a given time. This minimizesthe initial amount of diesel required for the refluxing process. Aspyrolysis occurs at the lower sections of the pit, the pressure islowered and the coal or shale oil that is generated adds to therefluxing supply and establishes an incrementally higher reflux point inthe pit.

The boiling point distribution of the refluxing oil may also be variedby adjusting the pressure in the pit to achieve different heatingtemperatures if desired. The boiling temperature can be increased byelevating the pressure. The optimum pressure may be in the range of 1-3atm. For instance, hexadecane has a boiling point of ˜300° C. at 1 atm.At 2 atm., the boiling point increases to ˜350° C. By operating the pitat elevated pressures and temperatures, at the end of pyrolysis,hydrocarbon liquids remaining in the pit may be flashed to vapor bylowering the pressure of the pit.

In some embodiments, production pipes may be located in the pit or pile.Liquids are produced from the production pipe at the bottom and gasesproduced from the production pipe at the top of the pit or pile.

The top of the seal may be covered with a thermally insulating layer ofrefractory ceramic or clay or combinations of the two to limit heatlosses to the environment.

Additional pits may be constructed adjacent to existing pits (FIG. 12).Surface facilities such as processing equipment and heating systems maybe shared between multiple pits, thereby reducing the total surfacefootprint and capital expenditures.

The pipes may be constructed with Grayloc fittings so that they can beeasily removed. The pipes are sloped at an angle between 0.1-2° (seeFIG. 24) so that the molten salt can self-drain from the pipes and othermolten salt equipment into the lower molten salt container which may beplaced below grade on the down flow side.

Thermal Conduction Heating of Pit or Pile with Molten Salt HeatersEmbedded in Walls

FIGS. 2, and 13-18 relate to systems for pyrolysis ofhydrocarbon-containing rocks (e.g. mined oil shale or mined coal or tarsands) arranged in a rock bed in an interior of an excavated enclosureby wall-embedded heaters.

As shown in FIG. 2, a pit is first excavated. The pit may be lined withclay, such as bentonite, to render the bottom substantially impermeableto liquids and vapors. It may be desirable to choose a location wherethe surface geology is a naturally-occurring clay so that lining the pitwith clay is unnecessary. The pit may be constructed below grade levelusing earth-moving equipment well known in open pit mining operations. Ahard insulation layer such as a low density refractory ceramic(firebrick) may then be placed inside the clay barrier to reduce heatlosses to the surroundings. The walls of the pit are constructed of asealed metal structure, and heater pipes are embedded in the walls ofthe structure. The bottom of the heater walls extend into the layer ofclay, creating a seal at their intersection. The pit is then filled withpieces of oil shale, coal, tar sands, or other hydrocarbon-bearingmaterial.

A layer of insulation may be placed on top of the pit to reduce heatlosses. The pit is then covered with an impermeable layer, which issealed at the top of the wall to prevent the escape of-fluids or vapors.This layer may be clay, stainless steel lining, silicone rubber, orother impermeable material. The insulation at the top of the pit may belocated above or below the impermeable layer. If the layer of insulationis located below the impermeable sheet it is preferred that it becomprised of closed cell insulation to prevent liquids accumulating inthe insulation. It is preferred that this layer of insulation and theimpermeable seal be made of a flexible material such that it can berolled in place following the filling of the pit and unrolled uponcompletion of the pyrolysis process.

As shown in FIG. 14, multiple pits may be arranged side by side witheach pit sharing common heater walls with its neighboring pits. In thisarrangement, heat losses to the surroundings may be minimized.

The spacing between parallel heater walls is calculated to providethermal conduction heating of the hydrocarbon material in a time periodof about a few months. Typical heater wall spacing may be, for example,10 ft, 20 ft, 30 ft or greater spacing. The heater walls may be orientedalong the long axis of the pit or the short axis of the pit.

FIG. 13 shows for example the rise in temperature between two heaterwalls spaced 16.4 ft (5 m) apart and maintained at a constanttemperature of 500° C. The thermal diffusivity of the packed bed isassumed to be 0.004 cm²/sec. The pyrolysis of the hydrocarbon-bearingmaterial is complete in about 3 months when the temperature at themidplane rises to about 325° C. In addition to heat transfer by thermalconduction, natural convection of hot fluids within the packed bed willalso be effective and may shorten the heating time and may allow moreuniform heating in the packed bed.

The array of pits may be very long, for example 100 ft, 300 ft, 1000 ft,3000 ft or longer. The width of the pit may by 50 ft, 100 ft, 200 ft,300 ft or wider. The depth of the pit may be 10 ft, 30 ft, 50 ft, 100 ftor deeper. As shown in FIG. 14, an elevated structure supporting atwo-axis crane may be installed over the pits. A mechanical claw orscooper connected to the crane fills the pit with hydrocarbon-bearingmaterial transported to the site. Post-pyrolysis, the scooper emptiesthe pit into a container to be transported away from the site. The sitemay be located near a railroad line or road to facilitate thetransportation of material to and from the site of the pit by train ortruck. A conveyor belt may also be provided on site for conveyingmaterial to and from the pits.

For pits with widths that are substantially long, for example 100 ft orlonger, pillars to support the elevated tracks for the two-axis cranemay be located within the pit as shown in FIG. 15. The foundation forthe pillar may be surrounded by thermal insulation such as a refractoryceramic and may remain cool while the sounding pit is being heated. Amultitude of pillars may be located within the pit, which are sufficientto mechanically support the elevated tracks of the crane.

Heater pipes are embedded in the heater walls and radiantly heat thewalls to a nearly uniform temperature. The heater walls may beconstructed of a metal frame with metal sheeting covering the frame. Thesheeting may be welded along the joints to seal the wall from entranceof any produced vapors. The metal frame is designed and sized to handlethe load from the material in the pit without substantial deformation.The width of the wall is sufficiently large to accommodate the outerdiameter of the heater pipes, though sufficiently small to maintain alarge solid angle from the heater pipe to the wall, thereby increasingthe effectiveness of the radiant heat transfer. The surfaces of the pipeand the surfaces of the wall may also be roughened and blackened toincrease emissivity of the surfaces and hence the radiant heat transfer.The interior of the walls surrounding the heater pipes may acteffectively as a black body and maintain a substantial constant walltemperature.

Low molecular weight gases with good thermal conductivity such ashydrogen or helium may be added to the inner space of the wall tofurther enhance heat transfer from the heater pipes to the heater walls.

The space within the heater walls may also be filled with solid granularmaterial with high thermal conductivity, such as copper, aluminum oriron balls, to enhance heat transfer from the heater pipes to the heaterwalls.

Within the metal frame of the heater wall is a structure to support theheater pipes. The steel support frame may be lubricated with graphite orother high temperature lubricant to prevent sticking during the initialthermal expansion of the heater pipes. The heater piping may be loopedalong the long axis of the wall and may have multiple passes within thewalls before existing as shown in FIG. 16. Looping the piping within thewall naturally creates expansion loops to accommodate thermal expansion.

In some embodiments, horizontal heaters pipes arranged within the wallsmaintain a substantially constant preselected temperature along a longlength as shown in FIG. 16. The heater pipes may also be orientedvertically within the walls as shown in FIG. 2. The advantage of thehorizontal heater pipes are the long lengths and hence reduced number ofindividual heaters and pipe connections. An advantage of the verticalheater pipes is that they may be able to be easily replaced in an eventof a failure during the heating process.

The heaters may be pipes heated by a heat transfer fluids such as moltensalts, heated oils (such as Therminol VP-1 (Solutia) or DowTherm A (DowChemical), which are eutectic mixtures of biphenyl (C₁₂H₁₀) and diphenyloxide (C₁₂H₁₀O) with operating temperatures up to 400° C.)), and heatedgases such as CO₂, nitrogen, supersaturated steam or combustion air. Theheaters may also be electrical heaters such as Curie heaters or SECTheaters.

Molten salts are the preferred heat transfer fluids according to someembodiments. Molten salts have high heat capacity, low viscosity, andmay be operated to high temperatures, for example, 450° C., 550° C.,600° C., 700° C., or higher depending on the specific molten salt. Thisallows for high heat transfer from the circulating molten salt to theheater walls using reasonable pipe diameters and flow rates. Pipediameters may be, for example, 3″, 5″ or higher. Flow rates may be forexample, 1 kg/s, 5, kg/s, 15 kg/s or higher. The other heat transferfluids (e.g. oils or gases) may be used for preheating the pipes abovethe melting point of the molten salt used in this invention.

The molten salt may comprise nitrate or nitrite salts such as HiTecsalt, HiTec XL, Solar Salt, etc. The molten salt may also comprisecarbonates, chlorides, or fluoride salts. The molten salts may be asingle, binary, ternary, quaternary or other mixture of compounds. Themolten salt may be chosen to have a maximum use temperature of 375° C.or higher.

As shown in FIG. 16, the hot molten salt is fed into the heater pipesfrom a molten salt heat delivery system. The molten salt container andthe external piping between them are insulated and heat traced toprevent heat losses and freezing of the molten salt. There is a pumplocated in the molten salt container that pumps the molten salt to afurnace that heats the molten salt and circulates the molten saltthrough the heater pipes in the walls. The heating of the furnace may beachieved using processed gas, natural gas, coal, or oil. The heating gasmay be gas produced from the process that has been treated to removeundesirable components such as hydrogen sulfide, carbon monoxide andcarbon dioxide, and separate valuable natural gas liquids and hydrogen.The hydrogen gas may be utilized in the hydrotreating facility forupgrading the oil produced. The hydrogen sulfide may be treated in aClaus plant to make elemental sulfur and the sulfur may be used toproduce fertilizer.

Counter-current flow between adjacent heater pipes in the same wallhelps provide uniform heating to the pit. The heater piping may belooped inside the pit so that the exterior piping manifold has fewerconnections with fewer chances of leaks

Molten salt heat delivery systems can achieve very high thermalefficiencies, for example, 80-90%, if the furnaces are multipass and theincoming gases are preheated by the exhaust gases. The longer the lengthof the heater piping in the pit compared to the insulated sectionoutside the pit, the more thermally efficient the molten salt heatersbecome. If the length of the heater in the pit is, for example, tentimes the length of the insulated section outside the pit, the overallthermal efficiency may approach the furnace efficiency.

Gases for the molten salt furnaces may also be preheated by passing thegases through piping in previously pyrolyzed pits that have not cooledyet.

As shown in FIG. 16, a single molten salt heating system may be sharedbetween multiple pits, thereby reducing the total surface footprint andcapital expenditures. Liquid and gas treatment facilities may also beshared by multiple pits.

The pipes from a non-heated pit may be preheated using a heat transferfluid from one of the adjacent piles or pits. Alternatively, a gascombustor can be used to blow hot combustion gases through the pipes forpreheating. Electrical heating of the pipes using Joule heating, skineffect heating, or induction heating, can also be used.

The heat injection rate from the wall into the pit may be 500 W/m², 1000W/m² or higher. The heat injection from a single heater pipe may be 500W/ft, 1000 W/ft or higher, depending on the temperature of the heattransfer fluid and the diameter and spacing of the heater pipes. Thetemperature of the heat transfer fluid in the heater pipes may be in therange 400-700° C. or 500-600° C., or preferably about 550° C. Theoptimal spacing between heater pipes may be determined by numericalsimulations using a computer program such as STARS (CMG, Calgary) or bypilot experimentation. The spacing of the heater pipes may be, forexample, 5 ft, 10 ft, or greater. The thickness of the wall may be, forexample, 0.5 ft, 1.0 ft, 1.5 ft or greater.

The heater walls may also be heated by using boiling, reflux andcondensation as the heating method. As shown in FIG. 17, horizontalpipes heated by circulating molten salt may be located in a lowersection of the wall—e.g. immersed in a reservoir of working fluid. Theworking fluid with a boiling point near the desired operatingtemperature (350-700° C.) fills the space inside the wall to a levelcovering the heater pipes. The heater pipes boil the working fluid, andthe vapors condense on the walls, thereby imparting the heat ofvaporization and heating the wall to a nearly uniform temperature.

The working fluid for the desired operating temperature range of350-700° C. may be fluids such as synthetic oils, molten salts, ormolten metal. This invention preferably utilizes synthetic oils such asTherminol VP-1 (Solutia) or DowTherm A (Dow Chemical) as the workingfluid. These oils have a boiling points approaching 400° C. whenpressurized up to 150 psi. When operating at the higher temperatureranges, the inner side of the walls may be coated with coke inhibitorssuch as silicates to prevent scale from forming.

The gas pressure in the pit may be maintained at atmospheric pressure orslightly elevated pressures (e.g. 1 bar gauge). The higher the gaspressure during pyrolysis, the higher quality of the oil and gasproduced. The gas pressure that can be maintained in the pit may bedetermined by the quality of the seal of the impermeable cover. Highergas pressures in the pit improve the oil qualities but increase thepossibility of gaseous leakage and odors from the pit. Alternatively, aslight vacuum may be applied through the gas production piping tocollect the vapors. This reduces the chances for leakage of odors fromthe pit but may result in a somewhat lower quality of oil product.

In a second embodiment, the hydrocarbon-bearing material is not directlyfilled into the pit but rather it is transported to the facility inspecially designed reusable shipping containers by rail or truck. Thecontainers may have sizes of 8×9.5×48 ft or larger. The containers arelowered into the pit and arranged into a rectangular array between thewalls as shown in FIG. 18. Between each heater wall the containers maybe arranged in a single or in multiple rows. These rows may be amultitude in both width and height.

An insulating blanket may be rolled over the top of the containers aftera row of heaters is placed in the pit. This row may then be heated bythe two adjacent heater walls, bringing the material in the containersto pyrolysis temperatures. Thermally conductive material may be placedbetween adjacent containers to enhance heat transfer between thecontainers. The liquids and gases are produced through a port on the topof the containers and treated at an onsite location. As successive rowsof containers are loaded into the pit, heating of the new row commences.After a row is fully pyrolyzed in ˜3-4 months, the containers areallowed to cool. The containers with post-pyrolysis material are thenremoved from the pit and transported out of the facility.

The containers used in the pits may be constructed from a high strengthalloy with good high temperature corrosion resistance such as 347Hstainless steel. The corners of the containers are rounded to reducestress concentrations during the multiple thermal cycling of thecontainers.

In order to minimize costs, the containers used for heating in the pitsmay also be different than the shipping containers. In this case thepost-pyrolysis material may be transferred from the heating containersto the shipping containers. The shipping containers may then be ofstandard steel construction.

Upgrading Coal

The type of coal utilized for this invention is preferably in the rangeof vitrinite reflectance R_(o) between 0.45 and 0.9, most preferablybetween 0.5 and 0.8. This range of coal types includes sub-bituminous A,high volatile bituminous C, B, and A, and medium volatile bituminouscoal. These types of coal have high volatiles and low moisture content.During pyrolysis the hydrocarbon fluids produced comprise light oilswith API gravities above 30° API and hydrocarbon gases with maximumC₁-C₄ content and minimum CO₂. Low sulfur and low ash coals arepreferred.

Production ports may be located at the top of the pit or pile andpenetrate through the impermeable seal and insulation. Fluids areproduced in the vapor phase through the top port, and the liquids andgases are separated. The API gravity of the produced oil may be 30° APIor higher. The NGL (natural gas liquids) such as propane and butane maybe separated from the methane and ethane gases because of the higheconomic value of NGL. Hydrogen may also be separated from the producedgases and used in upgrading of the produced oils.

FIG. 4B is a flow chart of a method for upgrading mined coal within anenclosure (e.g. an excavated enclosure). In step S241, pieces of coalare introduced into the enclosure. In step S245, the coal within the pitand/or container is heated over a sufficient amount of time so that: (i)kerogen of the coal is pyrolyzed into hydrocarbon pyrolysis formationfluids which may be recovered from the enclosure (see step S249); and(ii) the coal itself is upgraded to increase the coal vitrinitereflectance and/or to reduce the fraction of volatile matter and/or toincrease a fraction of carbon and/or reduce a moisture content and/or toincrease a heat content density by weight.

In step S243, the upgraded coal is removed from the enclosure.

In one non-limiting example, (i) the ‘input’ coal introduced in stepS241 is primarily bituminous coal (for example, high volatile bituminouscoal) and/or sub-bituminous coal and/or primarily coal whose reflectanceis less than 1.2 or less than 1.0 or less than 0.8 or less than 0.6 orless than 0.4 and (ii) the upgraded coal has one or more properties ofanthracite coal and/or is anthracite coal. Towards this end, in someembodiments, it is possible to heat the coal to achieve specifictime-temperature histories.

For example, it is possible to heat this ‘input coal’ over a‘multi-month’ time period (e.g. for at least 2 months or at least 2.5months or at least 3 months or at least 3.5 months or at least 4 monthsor at least 5 months or at least 6 months or at least 7 months), suchthat the temperature of the heated coal exceeds a MINIMUM_TEMP (e.g. forexample, at least 350 degrees C. or at least 375 degrees C. or at least400 degrees C. or at least 425 degrees C. or at least 450 degrees C. orat least 475 degrees C. or at least 500 degrees C. or at least 550degrees C. or at least 600 degrees C.) most of the time or substantiallyall of the time during the ‘multi-week’ or ‘multi-month’ time period.

In some embodiments, a maximum temperature of the bed of coal during themulti-month time period is at most 800 degrees C. or at most 700 degreesC. or at most 600 degrees C.

In some embodiments, the ‘upgraded coal’ removed in step S253 (i) has areflectance of at least 2.5 or at least 2.75 or at least 3.0 or at least3.25 or at least 3.5 and/or (ii) comprises (i.e. by total weight or byweight on an ash-free basis) less than 12% or less than 10% or less than8% or less than 6% volatile matter and/or (iii) has a heat content (i.e.by total weight or by weight on an ash-free basis) that exceeds 33,000kJ/kg or that exceeds 33,500 kJ/kg or that exceeds 34,000 kJ/kg or thatexceeds 34,500 kJ/kg and/or that exceeds 35,000 kJ/kg and/or thatexceeds 35,500 kJ/kg and/or (iv) comprises (i.e. by total weight or byweight on an ash-free basis) less than 8% or less than 6% or less than4% or less than 3% or less than 2.5% sulfur and/or (v) comprises (i.e.by total weight or by weight on an ash-free basis) at least 88% or atleast 89% or at least 90% or at least 91% carbon and/or (v) has one ormore properties associated with so-called ‘anthracite coal.’

There is no limitation on the features (e.g. physical structure or anyother features) of the container and/or pit in which the coal-upgradingroutine of FIG. 1 is carried out.

It is noted that the time-temperature history required to achievingspecific reflectance property and/or other property related to‘upgrading coal’ or ‘upgrading a rank of coal’ may at least partiallydepend upon the type of and/or the properties of the (i) ‘input’ coaland which is subjected to the coal-upgrading process and the (ii)upgraded coal resulting from the process.

The skilled artisan is directed to WO/2003/036035 entitled “IN SITUUPGRADING OF COAL” and U.S. Pat. No. 6,969,123 entitled “Upgrading andmining of coal” both of which are incorporated herein by reference intheir entirety. These patent documents describe the upgrading of bitumencoal to anthracite coal in situ. It is now disclosed that similarconditions may be replicated within an enclosure so as to economicallyexploit the upgraded coal.

As illustrated in FIG. 19, in some embodiments, longer processing timesare required when operating at lower temperatures (i.e. as evidenced bythe ‘negative’ slopes illustrated in FIG. 19) and/or when upgrading to a‘higher ranked coal and/or when employing a ‘lower-ranked’ startingmaterial/‘input’ coal.

The example of FIG. 19 illustrates linear curves—this is a simplifiedexample is appreciated that the shape of the curves may differ.

In the example of FIG. 19, the coal rank ‘X2’ exceeds the coal rank ‘X1’while the coal rank ‘Y2’ exceeds the coal rank ‘Y1.’ FIG. 19 is ahypothetical example, and unless otherwise indicated, is not intended aslimiting in any manner. For example, there is no requirement that the‘curves’ are linear and/or parallel to each other.

FIG. 20A illustrates the time dependencies of various measurabletime-dependent properties as a function of time in some embodimentsrelating to the any coal-upgrading routine disclosed herein. FIG. 20Billustrates that rate at which liquid and gaseous hydrocarbons are fromthe coal. Both FIGS. 20A-20B relate to hypothetical examples, and unlessotherwise indicated, no feature(s) of FIG. 20A and/or FIG. 20B isintended as limiting. Nothing in FIGS. 20A and/or 20B is intended as‘to-scale’ unless indicated otherwise.

In some embodiments, a bed of rocks is formed from bituminous coal, anda majority of the bed of rocks is maintained (i.e. under anoxicconditions) at a temperature of at least 375 degrees Celsius or of atleast 380 degrees Celsius or of at least 385 degrees

Celsius or of at least 390 degrees Celsius for a least 1 week or atleast 2 weeks or at least 1 month or at least 2 months or at least 3months or at least 6 months.

In the example of FIG. 20A, vitrinite reflectance and bulk temperatureof the coal, and heater power level is illustrated for one examplerelating to the upgrading of mined coal under anoxic conditions withinan enclosure (e.g. an excavated enclosure). During an earlier period oftime (TIME_PERIOD_(—)1), most kerogen of the coal is pyrolyzed intocondensable hydrocarbon pyrolysis fluids (referred to informally as‘liquids’), while in a latter time period (i.e. TIME_PERIOD_(—)2), mostnon-condensable hydrocarbon pyrolysis formation fluids are generated. Ata later period in time (TIME_PERIOD_(—)3), despite the fact that most ifnot substantially all pyrolysis fluids have been generated from coalkerogen, it is possible to continue to deliver significant power to thecoal of the coal bed so as to continue to upgrade the coal. From thepoint of view of economic pyrolysis fluid recovery, delivery of thermalenergy to the coal during TIME_PERIOD_3 may be unnecessary. However, itis now disclosed that this is useful for upgrading mined coal.

Reference is made once again to FIG. 20A. At different times during thecoal upgrade process, local coal physical and/or chemical properties mayvary at different locations within the container and/or pit. One coalproperty that may be monitored (e.g. by employing removing coal fromthen pit and/or container to sample the coal and/or by employing afiber-optic system to monitor the coal within the pit and/or container)at different times is the vitrinite reflectance. As illustrated in FIG.20B at times t₀-t₅ the temperature in a particular location and/or thebulk-averaged vitrinite reflectance and/or maximum temperature withinthe pit and/or container may respectively be written as R₀-R₅. In someembodiments when the input coal is so-called high volatile bituminouscoal, R₀ is at most 1.2 or at most 1.0 or at most 0.8 or at most 0.6 orat most 0.4. In some embodiments, R₂ is at most 1.6 or at most 1.4 or atmost 1.2. In some embodiments, R₄ is at most 2.5 or at most 2.0 or atmost 1.8 or at most 1.6. In some embodiments, R₅ is at least 2.4 or atleast 2.6 or at least 2.8 or at least 3.0 or at least 3.2 or at least3.4 or at least 3.6 or at least 3.8 or at least 4.0

Pre-Processing of Coal

Pretreatment of the coal may be desirable to produce the best qualitypost-pyrolysis coal. Pretreatment of the initial coal may include waterwashing to remove ash and fines. The coal pieces may be pre-sized toselect a size range that will easily pack in the pit to achieve apacking with high vertical permeability.

In some embodiments, the coal is pre-processed before heating to reducethe ash content-for example washing the coal (or alternativelymechanical agitation) to reduce the ash content (i.e. as a ‘bulkproperty’ of coal particles) of the coal. In some embodiments, beforethe pre-processing the ash content before exceeds 10% or exceeds 15% orexceeds 20%. In some embodiments, the ash content is reduced to no morethan 7% or no more than 6% or no more than 5% or no more than 4% or nomore than 3%. In some embodiments, the ash content is reduced by atleast 20% or at least 30% or at least 40% or at least 50% or at least60% or at least 70% or at least 80%.

The flotation step of removing inorganic matter could also be donebefore the bituminous coal is placed in the pit, as well as after.Removing ash may obviate the need to heat the inorganics to hightemperatures.

The pre-processing may be carried out in any time or in any location.For example, the pre-processing may be carried out ‘on site’ near thecontainer or pit or off-site.

Post-Processing of Coal After Pyrolysis

After pyrolysis, the top seal of the pit or pile may be opened to removethe devolatilized coal or oil shale. This coal may be more valuable thanthe initial coal because it has higher carbon content, higher calorificvalue, ultra lower moisture and volatiles, and lower sulfur andnitrogen. After removing the post-treatment coal or oil shale, the pitcan be refilled with fresh coal or oil shale for the next pyrolysisoperation. The post-pyrolysis coal or oil shale may also be steamcleaned in the pit while still above 100° C. to achieve both steamstripping and more rapid cooling of the coal or oil shale.

For example, a majority of coal within the pit and/or container may becooled by at least 150 degrees or at least 200 degrees C. or at least300 degrees C. within a period of time that does not exceed 1 month ordoes not exceed 2 weeks or does not exceed 1 week or does not exceed 3days or does not exceed 2 days or does not exceed 1 day or does notexceed 12 hours or does not exceed 6 hours.

In some embodiments, it is possible to carry out the cooling of the coalby so-called steaming of the coal—i.e. introducing liquid water into thecontainer and/or pit to ‘quickly’ cool the coal to a temperature that is(i) less than 150 degrees C. or less than 125 degrees C. or less than110 degrees C. and (ii) greater than 80 degrees C. or greater than 90degrees C. or greater than 95 degrees C. By ‘steaming’ the coal it ispossible to simultaneously (i) wash out impurities of the coal (ii)benefit from a ‘quick cooling of the coal’ while (iii) keeping the coalsubstantially dry.

The coal may be removed from the container and/or pit at a temperaturethat is about 100 degrees C. or allowed to cool further before removingin step S133.

FIG. 22B relates to a hypothetical example where the water flow rate ofliquid water into the pit is dramatically reduced (e.g. by at least 80%or at least 90%) at a time when the coal temperature approached 100degrees C.

After pyrolysis, the coal may be removed from the pit using buckets thatscoop the coal between the columns of heater pipes. The coal may beupgraded during the pyrolysis process because water and volatiles havebeen removed. The post-pyrolysis coal may have higher carbon content,higher calorific value, lower sulfur, oxygen and nitrogen, highervitrinite reflectance, and lower ash than the mined coal. Thus thispremium coal product may be sold at a higher price than the initialmined coal.

The temperature, time of heating, and pressure of the coal pit may beadjusted to achieve the greatest value added by upgrading the coal todifferent desirable grades. For example, a high value ultralow volatileanthracite coal may be produced suitable for PCI sintering formetallurgical coking. In general, anthracite coal may be more valuablethan lower grades of coal.

A Discussion of FIGS. 23-24

FIG. 23 is a cross section of a horizontal molten salt heating systemthat traverses a bed of rocks.

As shown in FIG. 24, the hot molten salt is fed from one side of the pitwhere the molten salt container is located. The molten salt containersand the external piping between them are insulated and heat traced toprevent heat losses and freezing of the molten salt. There is a pumplocated in the molten salt container that pumps the molten salt to afurnace that heats the molten salt and circulates the molten saltthrough the heater pipes in the pt. The heating of the furnace may bedone using processed gas, natural gas, coal, or oil. The heating gas maybe gas produced from the process that has been treated to removeundesirable components such as hydrogen sulfide, carbon monoxide andcarbon dioxide, and separate valuable natural gas liquids and hydrogen.The hydrogen gas may be utilized in the hydrotreating facility forupgrading the oil produced. The hydrogen sulfide may be treated in aClaus plant to make elemental sulfur.

A similar molten salt heat delivery system (tank, furnace, pump, andpiping manifold) may be placed on the opposite side of the pit to reheatthe cold molten salt coming from the pit and recirculate hot molten saltin the opposite direction. Counter-current flow between adjacent heaterpipes helps provide uniform heating to the pit. Instead of a secondmolten salt heat delivery system, the heater piping may be looped insidethe pit so that the exterior piping manifold has fewer connections withfewer chances of leaks.

In geographical regions of high average solar intensity, solar radiationmay be used to heat the heat transfer fluid using solar collectors suchas parabolic troughs, parabolic dishes, or power towers. Parabolictrough solar collectors are preferred as the synthetic oil used tocollect the solar heat can also function to transfer the heat to thepit. Furthermore, the operating temperature range of 350-390° C. matchesthe temperature range required for the pit. To accommodate daily solarintermittency, energy may be stored in high temperature molten salttanks and sized accordingly.

After pyrolysis is complete, the heaters are de-energized and the oil inthe lower section is drained from the pit. Some coal or oil shaleliquids may remain in the pores of the matrix and may be evaporated andcollected by circulating gases such as methane, CO₂, or nitrogen throughthe matrix. These gases may be part of a closed-loop heat exchangerinvolving multiple pits whereby the heated gas is circulated through apre-pyrolysis coal or oil shale in an adjacent pit, simultaneouslycooling down the post-pyrolysis pit and preheating the adjacent pit,thereby increasing the thermal efficiency of the process even further.

In the description and claims of the present application, each of theverbs, “comprise” “include” and “have”, and conjugates thereof, are usedto indicate that the object or objects of the verb are not necessarily acomplete listing of members, components, elements or parts of thesubject or subjects of the verb.

All references cited herein are incorporated by reference in theirentirety. Citation of a reference does not constitute an admission thatthe reference is prior art.

The articles “a” and “an” are used herein to refer to one or to morethan one. (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

The term “including” is used herein to mean, and is used interchangeablywith, the phrase “including but not limited” to.

The term “or” is used herein to mean, and is used interchangeably with,the term “and/or,” unless context clearly indicates otherwise.

The term “such as” is used herein to mean, and is used interchangeably,with the phrase “such as but not limited to”.

The present invention has been described using detailed descriptions ofembodiments thereof that are provided by way of example and are notintended to limit the scope of the invention. The described embodimentscomprise different features, not all of which are required in allembodiments of the invention. Some embodiments of the present inventionutilize only some of the features or possible combinations of thefeatures. Variations of embodiments of the present invention that aredescribed and embodiments of the present invention comprising differentcombinations of features noted in the described embodiments will occurto persons skilled in the art.

1. A method of heating hydrocarbon-containing rocks comprising: a.introducing the hydrocarbon-containing rocks into an interior region ofan excavated enclosure to form a bed of rocks therein; b. maintaining areservoir of hydrocarbon liquids substantially at the bottom of theinterior region of the excavated enclosure; and c. heating thehydrocarbon liquids of the reservoir so as to maintain a hydrocarbonreflux loop within the interior region to convectively heat thehydrocarbon-containing rocks. 2-3. (canceled)
 4. The method of claim 1wherein the interior region is maintained under anoxic conditions duringthe heating.
 5. The method of claim 1 wherein kerogen or bitumen of therocks are pyrolyzed, the hydrocarbon reflux loop supplying at least aportion of the thermal energy required to pyrolyze kerogen or bitumen ofthe rocks.
 6. The method of claim 1 wherein the reflux loop verticallyspans at least a majority of the rock bed and/or of the interior regionof the excavated enclosure.
 7. The method of claim 1 wherein liquidhydrocarbon vapor of the reflux loop condenses primarily above the rockbed and/or substantially at a top thereof.
 8. The method of claimwherein a majority of the hydrocarbon fluid flow of the reflux looppasses via one or more vertical chimneys that substantially verticallytraverse the rock bed.
 9. The method of claim 8 wherein the verticalchimney passes through an interior of the rock bed.
 10. The method ofclaim 8 wherein wall(s) of the vertical chimney are liquid-tight. 11.The method of claim 8 wherein wall(s) of the vertical chimney are heatconductors to facilitate conductive heat transfer from (i) hydrocarbonfluids migrating within the vertical chimney to (ii) rocks of the bed.12. The method of claim 1 wherein thermal energy supplied by the refluxloop is sufficient to significantly raise a temperature of at least onelocation at the top of the rock bed.
 13. The method of claim 1 whereinthe heater(s) are immersed heaters located within a reservoir ofhydrocarbon liquid. 14-19. (canceled)
 20. A method of heatinghydrocarbon-containing rocks within an excavated enclosure comprising:a. arranging the hydrocarbon-containing rocks into rock bed within theenclosure so that one or more substantially vertical conduitssubstantially vertically traverse the rock bed; b. respectivelymaintaining lower and upper hydrocarbon liquid reservoirs at upper andlower elevations, the lower elevation being substantially at the bottomof the enclosure and substantially below the rock bed, the upperelevation being above or substantially at the top of the rock bed,wherein the upper hydrocarbon liquid reservoir is supplied primarily byboiling of hydrocarbon liquids of the lower reservoir so that vaporsformed therefrom substantially vertically traverse the rock bed andcondense into liquid of the upper reservoir, wherein at least somethermal energy for the pyrolysis is supplied by convective heat transferfrom downward movement of hydrocarbon liquid through the rock bed fromthe upper reservoir to the lower reservoir.
 21. The method of claim 20wherein a floor of the upper reservoir includes a plurality of voidsthrough which hydrocarbon liquids flow downwards into the hydrocarbonbed.
 22. The method of claim 20 wherein the voids are distributed overthe hydrocarbon bed so as to horizontally substantially evenlydistribute downward liquid flow from the upper reservoir into the rockbed. 23-63. (canceled)
 64. An coal upgrading method comprising: a.introducing pieces of coal into an excavated enclosure to form a rockbed therein, a substantial majority of the coal being bituminous coalhaving vitrinite reflectance of at most 1.8%; b. heating the coal of therock bed so that (i) an average temperature of the rock bed ismaintained between 250 degrees Celsius and 400 degrees Celsius for atleast one week; and (ii) a majority of the bituminous coal is upgradedinto anthracite coal having a vitrinite reflectance of at least 2.5%.65. The method of claim 64 wherein a pressure/temperature history of thecoal is regulated so as to maximize a rank of the heated coal.
 66. Themethod of claim 64 wherein a high value ultralow volatile anthracitecoal is produced.